Stainless Steel Coil Tube — HVAC Fan Coil Unit Application Grade
Product Code: JX-ST-229 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州继兴金属材料有限公司)
1. Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered coiled tubing product specifically designed for integration into Fan Coil Units (FCU) within commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) systems. Unlike conventional carbon steel or copper coil tubes, the stainless steel variant offers superior corrosion resistance, extended service life, and enhanced hygiene performance—particularly critical in dehumidification-intensive applications where condensation and moisture accumulation are prevalent.
This product is manufactured in compliance with international standards and is engineered to withstand prolonged exposure to humid environments, chemical condensates, and thermal cycling conditions inherent in fan coil unit operations. The coil tube serves as the primary heat exchange medium, facilitating efficient thermal transfer between the refrigerant/coolant and the airstream.
Key Application Context: As demonstrated in experimental research on fan coil unit dehumidification performance, stainless steel coil tubes exhibit superior moisture management characteristics compared to standard materials, reducing microbial growth risk and maintaining consistent heat exchange efficiency over extended operational cycles.
2. Material & Properties
2.1 Material Composition
The coil tube is fabricated from Stainless Steel (SS) with the following primary grades available:
- AISI 304 (UNS S30400): Austenitic stainless steel containing a minimum of 18% Chromium (Cr) and 8% Nickel (Ni). This grade offers excellent general corrosion resistance and is the preferred selection for most HVAC applications.
- AISI 316 (UNS S31600): Enhanced austenitic grade with an additional 2–3% Molybdenum (Mo), providing superior resistance to chloride-induced pitting corrosion—ideal for coastal or high-humidity environments.
- AISI 316L (UNS S31603): Low-carbon variant of 316 with carbon content below 0.03%, offering improved weldability and resistance to intergranular corrosion.
2.2 Mechanical & Physical Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa (304) / ≥ 515 MPa (316) | ASTM A213 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ASTM A213 |
| Elongation (延伸率) | ≥ 40% | ASTM A213 |
| Thermal Conductivity (导热系数) | 14.9 – 16.3 W/(m·K) | ASTM E1225 |
| Corrosion Resistance (耐蚀性) | PASS — 72-hour Salt Spray Test (ASTM B117) | ASTM B117 / GB/T 10125 |
| Operating Temperature Range (工作温度范围) | −196 °C to +870 °C | — |
| Hygienic Surface Finish (卫生表面) | Ra ≤ 0.8 μm (Electropolished available upon request) | ISO 15835 |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) / 外径 | 6.0 mm, 7.0 mm, 8.0 mm, 9.52 mm, 12.0 mm (custom sizes available) |
| Wall Thickness (WT) / 壁厚 | 0.5 mm – 1.5 mm (tolerance: ±10%) |
| Coil Diameter / 盘管直径 | 100 mm – 600 mm (configurable per FCU design) |
| Coil Length / 盘管长度 | Up to 50 meters per continuous coil (spool delivery) |
| Surface Treatment / 表面处理 | Pickled & Passivated (酸洗钝化); optional electropolishing |
| Forming Method / 成型方式 | Continuous cold-rolling & precision coiling |
| Heat Treatment / 热处理 | Solution annealing at 1050 °C – 1150 °C, water quench |
| Dimensional Tolerance / 尺寸公差 | OD: ±0.1 mm; WT: ±10%; Straightness: ≤ 1.5 mm/m |
| End Preparation / 端部处理 | Beveled ends (30° chamfer) for brazing or mechanical connection |
| Packaging / 包装 | Wooden crate or steel drum with moisture-proof wrapping |
| Delivery Form / 交货形式 | Coiled (盘管) or cut-to-length sections |
| Standards Compliance / 标准 | ASTM A213/A213M, GB/T 12771, EN 10216-5, JIS G3459 |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection (原材料筛选): High-purity stainless steel strip is sourced from certified mill suppliers with full traceability documentation (Mill Test Certificate / MTC) and verified chemical composition.
- Cold Rolling & Forming (冷轧成型): The steel strip undergoes precision cold-rolling to achieve the specified wall thickness and outer diameter. Multi-stand rolling mills with hydraulic gap control ensure dimensional consistency within tight tolerances.
- Solution Annealing (固溶退火): The formed tube is heated to 1050–1150 °C in a controlled atmosphere furnace to dissolve carbides, restore full austenitic microstructure, and relieve residual stresses from cold working. Rapid water quenching follows to lock in the desired grain structure.
- Pickling & Passivation (酸洗钝化): The annealed tube is subjected to acid pickling (typically nitric acid + hydrofluoric acid blend) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide (Cr₂O₃) film on the surface. This step is critical for ensuring long-term corrosion resistance.
- Precision Coiling (精密盘绕): The tube is coiled onto a mandrel using a CNC-controlled coiling machine. Uniform tension control prevents distortion, ovality, or kinking during the forming process. The resulting coil geometry is optimized for maximum heat exchange surface area within the compact FCU housing.
- Quality Inspection (质量检测): Each batch undergoes comprehensive inspection including:
- Chemical composition verification (Optical Emission Spectrometry / OES)
- Dimensional measurement (OD, WT, straightness via laser scanning)
- Mechanical testing (tensile, hardness per ASTM E10)
- Visual inspection for surface defects, weld seams, and passivation quality
- Non-destructive testing (NDT) — eddy current or ultrasonic testing as required
- Packaging & Dispatch (包装发货): Coils are wrapped in moisture-proof material, secured with steel bands, and packed in wooden crates or steel drums to prevent mechanical damage and corrosion during transit.
5. Applications
The stainless steel coil tube is specifically engineered for demanding thermal management applications. Primary application domains include:
- Fan Coil Units (FCU) / 风机盘管机组: Serves as the core heat exchange element in both chilled water and hot water FCU systems. The stainless steel construction provides superior resistance to condensate corrosion compared to carbon steel alternatives, ensuring reliable dehumidification performance over the system's operational lifetime.
- Commercial HVAC Systems / 商用暖通空调系统: Deployed in office buildings, hotels, hospitals, and shopping centers where indoor air quality (IAQ) and system reliability are paramount.
- Residential Climate Control / 住宅气候控制: Used in concealed and ducted FCU installations in high-end residential properties.
- Industrial Process Cooling / 工业工艺冷却: Applicable in food processing, pharmaceutical manufacturing, and electronics cooling where hygienic and corrosion-resistant materials are mandated.
- Marine & Coastal HVAC / 海洋及沿海暖通: The 316/316L grades provide exceptional resistance to salt-laden atmospheric conditions.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and traceability:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering the full manufacturing and supply chain |
| ISO 14001:2015 | Environmental Management System — responsible manufacturing practices |
| ASTM A213/A213M | Standard specification for seamless austenitic stainless steel tubing for high-temperature service |
| GB/T 12771 | Chinese national standard for welded stainless steel tubes for fluid transport |
| EN 10216-5 | European standard for welded stainless steel tubes — part 5: austenitic and ferritic grades |
| JIS G3459 | Japanese Industrial Standard for welded stainless steel tubes for general service |
| Mill Test Certificate (MTC) | EN 10204 Type 3.1 certified — issued with each shipment, verifying chemical composition and mechanical properties |
| CE Marking | Conformity with European health, safety, and environmental protection standards |
7. Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel matrix provides exceptional resistance to condensate-induced corrosion, significantly outperforming carbon steel coil tubes in dehumidification-heavy applications. This translates to a service life of 15–25 years versus 5–8 years for conventional alternatives.
- Hygienic Surface Integrity: The pickled and passivated surface finish (Ra ≤ 0.8 μm) minimizes biofilm formation and microbial colonization, making it particularly suitable for hospital, pharmaceutical, and food-grade HVAC installations.
- Thermal Efficiency Retention: Unlike carbon steel, which develops rust-induced thermal resistance over time, stainless steel maintains consistent thermal conductivity throughout its service life, ensuring sustained dehumidification and cooling performance.
- Customization Capability: Flexible customization of OD, wall thickness, coil diameter, and coil length to match specific FCU OEM designs and project specifications.
- Full Traceability: Every batch is accompanied by a certified Mill Test Certificate (MTC) with complete material provenance and test data, ensuring supply chain transparency and regulatory compliance.
- Environmental Sustainability: Stainless steel is 100% recyclable and the manufacturing process adheres to ISO 14001 environmental management standards, contributing to sustainable building practices.
8. Technical Notes & Recommendations
Installation Note: When integrating stainless steel coil tubes into FCU assemblies, ensure all connecting fittings and braze alloys are compatible with austenitic stainless steel to prevent galvanic corrosion. Phosphorus-free copper brazing alloys are recommended. Avoid direct contact with carbon steel components without isolation.
Dehumidification Performance Note: Experimental research on fan coil unit dehumidification performance confirms that stainless steel coil tubes maintain lower surface temperatures under condensate conditions compared to carbon steel, resulting in more effective latent heat removal and improved moisture control in the airstream. This is attributed to the stable oxide layer preventing insulating rust formation on the tube surface.
For detailed technical data sheets, sample requests, or customized specification inquiries, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.